They will both perform the same as far as overclocking. The main differences between them is the Z68 units have on-board video and the ability to do SSD caching. Right now the prices are basically the same, so go for the Z68 board. Even if you don't intend to use those features, the option is there in case you change your mind in the future. If I was buying a LGA1155 motherboard right now I would get the ASUS P8Z68-V/GEN3. Getting a Gen3 board allows you to upgrade to Ivy Bridge when it becomes available next year.

They will both perform the same as far as overclocking. The main differences between them is the Z68 units have on-board video and the ability to do SSD caching. Right now the prices are basically the same, so go for the Z68 board. Even if you don't intend to use those features, the option is there in case you change your mind in the future. If I was buying a LGA1155 motherboard right now I would get the ASUS P8Z68-V/GEN3. Getting a Gen3 board allows you to upgrade to Ivy Bridge when it becomes available next year.